page_title: Frigate
section_title: Anti-submarine role
hierarchical_section_title: Frigate / Contemporary / Anti-submarine role
caption_attribution_description: English: HMS&#160;Somerset at Cape Trafalgar
context_page_description: A frigate is a type of warship, having various sizes and roles over time.
  In the 17th century, a frigate was any warship built for speed and maneuverability, the description often used being "frigate-built". These could be warships carrying their principal batteries of carriage-mounted guns on a single deck or on two decks. The term was generally used for ships too small to stand in the line of battle, although early line-of-battle ships were frequently referred to as frigates when they were built for speed.
  In the 18th century, frigates were full-rigged ships, that is square-rigged on all three masts, they were built for speed and handiness, had a lighter armament than a ship of the line, and were used for patrolling and escort. In the definition adopted by the British Admiralty, they were rated ships of at least 28 guns, carrying their principal armaments upon a single continuous deck – the upper deck – while ships of the line possessed two or more continuous decks bearing batteries of guns.
  In the late 19th century, the armoured frigate was a type of ironclad warship that for a time was the most powerful type of vessel afloat.
context_section_description: At the opposite end of the spectrum, some frigates are specialised for anti-submarine warfare. Increasing submarine speeds towards the end of World War II (see German Type XXI submarine) greatly reduced the margin of speed superiority of frigate over submarine. The frigate could no longer be slow and powered by mercantile machinery and consequently postwar frigates, such as the Whitby class, were faster.
  Such ships carry improved sonar equipment, such as the variable depth sonar or towed array, and specialised weapons such as torpedoes, forward-throwing weapons such as Limbo and missile-carried anti-submarine torpedoes such as ASROC or Ikara. Surface-to-air missiles such as Sea Sparrow and surface-to-surface missiles such as Exocet give them defensive and offensive capabilities. The Royal Navy's original Type 22 frigate is an example of a specialised anti-submarine warfare frigate.
  Especially for anti-submarine warfare, most modern frigates have a landing deck and hangar aft to operate helicopters, eliminating the need for the frigate to close with unknown sub-surface threats, and using fast helicopters to attack nuclear submarines which may be faster than surface warships. For this task the helicopter is equipped with sensors such as sonobuoys, wire-mounted dipping sonar and magnetic anomaly detectors to identify possible threats, and torpedoes or depth-charges to attack them.
  With their onboard radar helicopters can also be used to reconnoitre over-the-horizon targets and, if equipped with anti-ship missiles such as Penguin or Sea Skua, to attack them. The helicopter is also invaluable for search and rescue operation and has largely replaced the use of small boats or the jackstay rig for such duties as transferring personnel, mail and cargo between ships or to shore. With helicopters these tasks can be accomplished faster and less dangerously, and without the need for the frigate to slow down or change course.
caption: HMS Somerset of the Royal Navy. Type 23 frigates were built for anti-submarine warfare but are capable multi-purpose ships.[22]
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